Being pro-EU was just their way of saying "I'm not like Those People. I'm more sophisticated. I speak French, and I pronounce Italian names correctly."
If you were pro-EU because you appreciate specific benefits of EU membership, your rational response to the Referendum would have been to look for a second-best option, which preserves most of those benefits.
Very few did that.
But if you assume that it's about signalling, it makes sense.
That's why it didn't fly with most Remainers.
Now the wine store runs out of it, but they tell everyone: "We've got this totally unknown grape, which is quite similar in style, just less tangy, more easy-drinking."
This is the watershed moment...
If it's the taste you're after, you'll think, "Sure, I'll take that."
If it's the signal you're after, you won't be interested.
He doesn't get it, of course. Because they don't have it. But by making a lot of noise, he still manages to send his signal.